Trade everything. Make all concessions you give conditional on getting something in return preferably of a higher value.

Make them conditional: use conditional language such as “If you can do X for us then we would be able to do Y for you.”

Trading concessions. The language you might use depends on the circumstances. It is generally better to use third party conditional language

If you can do this for us, then we can do this for you. Or you could say although this is more aggressive and a little less win, we might be able to you this for you.

If you have a personal relationship and you are trying to make the negotiations friendlier. You might use “if you can do this me then I can do this for you”.

It is better to ask for what you want from them, before you mention what you can do for them. What you are trading. People tend to hear what is mentioned first. So if they hear you mention what you are going to concede first they may switch off to what you want in return.